Presentation
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Involvement of first-order thalamic nuclei in human language systems: Functional and structural correlates
Poster D117 in Poster Session D, Wednesday, October 25, 4:45 - 6:30 pm CEST, Espace Vieux-Port
This poster is part of the Sandbox Series.
Liu Mengxing1, Garikoitz Lerma-Usabiaga1,2, Pedro M. Paz- Alonso1,2; 1BCBL. Basque Center on Cognition, Brain and Language, 2Ikerbasque, Basque Foundation for Science
The cerebral cortex has been regarded as the key player in higher cognitive functions, including language. The subcortical structures, such as the thalamus, have been thought to have subordinate or negligible involvement in these functions. Despite lesion and functional neuroimaging evidence of thalamic involvement in language, the field of neurobiology of language is still debating the notion that the thalamus plays any role in language at all. Previously, the thalamus was understood as a simple transponder, relaying information in cortico-cortical and cortico-subcortical systems. These views have been extensively challenged over the last years. For example, the first-order relay thalamic nuclei, traditionally viewed as mere gateways to the cerebral cortex, are suggested to play a more integrative role in higher functions. Nevertheless, the role of the sensorimotor thalamic nuclei and their interactions with the cerebral cortex in language processing remains largely unknown. Different language systems heavily rely on distinct types of sensorimotor information (e.g., visual input for reading, auditory input for speech comprehension, and motor articulation for speech production), and it is expected that the involvement of the lateral geniculate nucleus (LGN), medial geniculate nucleus (MGN), and ventral lateral nucleus (VLN) may vary across these language systems. Here, we present the results from a large multimodal MRI study aimed at investigating the involvement of sensorimotor thalamic nuclei (LGN, MGN, VLN) in reading, speech comprehension and speech production. The analytical approach included an examination of the functional activation of these nuclei, and their functional and structural connectivity with cortical and cerebellar regions of the language network. To this end, 40 participants underwent MRI scanning and performed tasks associated with language comprehension and production processes. Along with linguistic stimuli, non-linguistic stimuli, such as scrambled visual pixels, scrambled speech sounds, and unintelligible sound production, were included as control conditions. Outside of the MRI, participants completed comprehensive behavioral testing to further examine functional and structural brain-behavior associations. Our results demonstrated greater engagement of the LGN, MGN, and VLN in both linguistic and non-linguistic tasks across the corresponding sensory modalities, compared to baseline. Furthermore, the functional activation of each task was specific to the examined first-order thalamic nuclei (e.g., LGN activation during reading but not during speech comprehension or speech production). Importantly, we observed stronger activation in language comprehension tasks for linguistic stimuli compared to non-linguistic stimuli. For instance, the LGN exhibited higher activation when reading real words than when viewing scrambled pixels. Additionally, task-related functional connectivity within visual, auditory and motor thalamocortical networks was associated with the respective language systems. Finally, statistically significant associations between functional, structural and behavioral data within each language system were observed in multiple regression models. In sum, our findings indicate a segregation in the implication of different human thalamic sensorimotor nuclei and their thalamocortical interactions in the main human language systems, indicating that their functional and structural properties significantly contribute to explain language behavior.
Topic Areas: Reading, Speech Perception